great imitator

Medspeak A nonspecific term for any condition that is difficult to diagnose due to its polymorphous presentation; the classic ‘great imitator’ is syphilis, which has a broad clinical palette, especially vis-à-vis the skin and central nervous system; lesser ‘great’ imitators include HIV infection, hypothyroidism, systemic lupus erythematosus, tertiary Lyme disease, pheochromocytoma
Rheumatology Systemic lupus erythematosus, see there

great imitator

Great imposter A nonspecific term for any condition that is difficult to diagnose due to its polymorphous presentation; the classic 'great imitator' is syphilis, which has a broad clinical palette, especially affecting the skin and CNS; more recent lesser 'great imitators include HIV, hypothyroidism, tertiary Lyme disease, pheochromocytoma. Cf Internists' tumor RheumatologySystemic lupus erythematosus, see there.